Comparison of the Anesthetic Effects of Alfaxalone Combined with Xylazine or Dexmedetomidine in Captive Formosa Serows (Capricornis swinhoei)

Abstract

Formosan serows are an endemic species in Taiwan. Alfaxalone, a γ-aminobutyric acid_A agonist, induces or maintains anesthesia in various veterinary species with reported potential adverse effects of respiratory depression and tachycardia. α2-Adrenoceptor agonists exert sedative and muscle relaxation effects, along with substantial cardiovascular adverse effects. Here, we aimed to evaluate the anesthetic effects of alfaxalone combined with xylazine or dexmedetomidine (AX vs. AD, respectively) in Formosan serows. In this randomized, masked study, AX was administered to four serows, and AD was administered to five serows intramuscularly via blow dart. The time and score of induction and recovery were recorded. Post-intubation, isoflurane was administered for maintenance anesthesia. Heart rate (HR), respiratory rate (RR), peripheral saturation of oxygenation (SpO₂), rectal temperature (RT), and end-tidal CO₂ (EtCO₂) were recorded every five to eight minutes. Atipamezole and tolazoline were administered to antagonize dexmedetomidine and xylazine post-procedure, respectively. Both combinations allowed smooth induction and recovery. The AD group exhibited significantly lower HR and SpO₂ and significantly higher RT and EtCO₂ than the AX group (both p < 0.01). The AD-treated serows exhibited notable muscle rigidity after induction and significant hypoventilation and hypoxemia during the procedure. Although alfaxalone combined with dexmedetomidine or xylazine can produce satisfactory induction and recovery in Formosa serows, notable hypoxemia and hypoventilation are induced by the alfaxalone-dexmedetomidine combination compared to the alfaxalone-xylazine combination.

Keywords: Formosan serow (Capricornis swinhoei); alfaxalone; anesthesia; hypoventilation; hypoxemia.

Figure 1

Timeline illustration of this study. The time points and associated events are shown. The measurement of physiological parameters was performed every 5–8 min after the first measurement of HR, SpO₂, and EtCO₂. EtCO₂, end-tidal CO₂; HR, heart rate; RR, respiratory rate; RT, rectal temperature; SpO₂, peripheral saturation of oxygenation.

Figure 2

Consort diagram for study design. AX, alfaxalone–xylazine; AD, alfaxalone–dexmedetomidine.

Figure 3

Induction time (A), induction score (B), recovery time (C), and recovery score (D) in Formosan serows administered alfaxalone-xylazine (AX) or alfaxalone-dexmedetomidine (AD).

Figure 3

Induction time (A), induction score (B), recovery time (C), and recovery score (D) in Formosan serows administered alfaxalone-xylazine (AX) or alfaxalone-dexmedetomidine (AD).

Figure 4

Peripheral oxygen saturation in Formosan serows administered alfaxalone-xylazine (AX) or alfaxalone-dexmedetomidine (AD). Time 0 indicates the moment after induction before intubation. Time 1 indicates the moment immediately after intubation, with subsequent time points set at 5-8 min intervals. Asterisks denote statistical differences between the AX and AD groups: * p < 0.05).

Figure 5

The heart rate of Formosan serows administered alfaxalone-xylazine (AX) or alfaxalone-dexmedetomidine (AD). Time 0 indicates the moment after induction before intubation. Time 1 indicates the moment immediately after intubation, with subsequent time points set at 5-8 min intervals. Asterisks denote statistical differences between the AX and AD groups: * p < 0.05. BPM, beats per minute.

Figure 6

The respiratory rate of Formosan serows administered alfaxaloneu-xylazine (AX) or alfaxalone-dexmedetomidine (AD). Time 0 indicates the moment after induction before intubation. Time 1 indicates the moment immediately after intubation, with subsequent time points set at 5-8 min intervals. Asterisks denote statistical differences between the AX and AD groups: * p < 0.05. BPM, beats per minute.

Figure 7

The rectal temperature of Formosan serows administered alfaxalone-xylazine (AX) or alfaxalone-dexmedetomidine (AD). Time 0 indicates the moment after induction before intubation. Time 1 indicates the moment immediately after intubation, with subsequent time points set at 5-8 min intervals. Asterisks denote statistical differences between the AX and AD groups: * p < 0.05.

Figure 8

End-tidal CO₂ of Formosan serows administered alfaxalone-xylazine (AX) or alfaxalone-dexmedetomidine (AD). Time 0 indicates the moment after induction before intubation. Time 1 indicates the moment immediately after intubation, with subsequent time points set at 5-8 min intervals. Asterisks denote statistical differences between the AX and AD groups: * p < 0.05.